Process and apparatus for conditioning the surfaces of metal bodies



March 2, 1943.

A. M. KELLER ETAL 2,312,418 I PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 10 Sheets-Sheet l R MI r\. II;

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\ n o I "31 Q INVENTORS I ARTHUR M. KELLER E I JAMES H. BUCKNAM w BY ALFRED J. MILLER $1 $1 ATTORN EY A. M. KELLER EI'AL 2,312,418 PROCESS AND APPARATUS FoR CONDITIONING THE SURFACES 0F METAL BODIES March 2, 1943.

Filed May 11, 1940 10 SheetS -Sheet 2 INVENTORS ARTHUR M. KELLER JAMES H. BUCKNAM BY ALFRED J. MILLER ATTORNEY March 2, 1943. A. M. KELLER EIAL PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 10 Sheets-Sheet 5 mas m R R ENE LKL SHC MKWM H T N H M R R O U U v "n H H A w TMT RAR AJA. Y Q% B JQS March 2, 3.

A KELLER EI'AL PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF NIETAL BODIES Filed May 11, 1940 10 $heet eet 4 57 50 J2 EK Q mmlllllllllnn,

INV ORS ARTHUR M. K ER JAMES H. KNAM BY ALFRED J. MILLER,

ATTORNEY March 2, 1943. A. M. KELLER EI'AL 2,312,418

PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 10 Sheets-Sheet 5 BY I ATTORNEY March 2,1943. A. M. KELLER ET AL F METAL BODIES PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES 0 Filed May 11, 1940 10 Sheets-Sheet 6 l l I VII/lllllllllll'l l I .IVIIIIIIIIIIIIII4 M R R E E L L LKL mEc V| KW M E M 5 m H 0 R D T VUSE T. NH R A MF RA AJA Y B O Mmh 2, 1943. A. M KELLER Em 2,312,418

PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 10 Sheets-Sheet 7 I 5/ WES 95 75 [i INVENTORS ARTHUR M. KELLER JAMES H. BUCKNAM BY ALFRED J. MILLER ATTORNEY 10 Sheets-Sheetfi LLER ATTORNEY March 2, 1943. A. M. KELLER EI'AL PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 March 2, 1943. A. M. KELLER ETAL 2,312,418

PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Filed May 11, 1940 10 Sheets-Sheet 9 'INVENTORS ARTHUR M. KELLER J ES H. BUCK M A RED J. MILL BY ma ATTORNEY Marh 2, 1943. A. M. KELLER ETAL 2,312,418

PROCESS AND APPARATUS FOR CONDITIONING THE SURFACES OF METAL BODIES Fi led My 11, 1940 10 Sheets-Sheet 1O [11 I ZZZ a1 a2 Z25 k 42 I I 250 I r226 Y+R i i 255 255 01 M 2 r I d2 21/ U El; 5 .5 211/ 2! g1 52 I55 W T] 5 L I I. :2 1 I F/RSTPOS/T/ON o o 0 o o o E] o o [1;] o o o o SECOND" oo oo o olzgloofilfioo THIRD o o o o |0 0| [0 0| [moi [0 0| 0 0. fl

FOURTH o o o 0 EE 0 o o o 5351 511a 5531 FIFTH o o o o o o o o o o o o e 0 OFF [E] E] o o o o 0 o o o o o o o INVENTORS ARTHUR M.I\EL.LER

JAMES H. BUCKNAM ALFRED J; MILLER ATTORNEY Patented Mar. 2, 1943 PROCESS AND APPARATUS FOR CONDI- TIONING BODIES SURFACES F METAL Arthur M. Keller, Livingston, James H. Bucknam, Cranford, and Alfred J. Miller, Garwood, N. 1., assignors to The Linda Air Products Company, a corporation of Ohio Application May 11, 1940, sci-m No. 334.510

20 Qaims. '(Cl. 148-9) This invention relates to blowpipe apparatus for thermally conditioning the surfaces of ferrous metal bodies and more particularly to blowpipe apparatus for thermochemically removing a layer of metal from the entire bottom surface of a steel body such as a billet, bloom, slab, or the like, to apparatus for removing scale from such surfaces and to a process of conditioning a surface of such metal body.

In the casting of steel ingots and during the hot rolling of steel, defects such as scale, cracks, seams, slag-inclusions and the like form on and in the surfaces of the steel bodies and cause imperfections in the finished rolled products. In

order to reduce the number of rejections of finished rolled products, the surface defects are generally removed before or during an intermediate stage of the rolling. Scale is commonly removed by pickling and other defects have often been removed by mechanically cutting or chipping away the defective surface metal. Handoperated blowpipes, commonly referred to as hand-deseaming blowpipes, are now also used for thermochemicaliy removing the defective surface metal adjacent each defect by effecting the combustion of the steel with oxygen. Recently, machines employing suitable blowpipe means have come into use for simultaneously thermochemically conditioning an entire surface of billets, and the like, or for simultaneously conditioning two opposite, substantially vertical side faces of such billets or for conditioning the top surface of slabs and the like. These machines may be used for conditioning steel shapes, either when cold or while they are at a rolling temperature -and are passing from one roll stand to another such as is commonly employed in a steel mill.

The present invention provides an apparatus for thermally conditioning the surface of a steel body such as a bloom or slab or for eliminating scale, and more particularly a machine for thermochemically removinga layer of surface metal from the entire bottom surface of the body during a single pass, preferably while the steel body is moving along a roll table from one rolling operation to another. A multiple nozzle blowpipe head producing high-temperature preheating flames and a composite sheet-like oxygen stream substantially equal in width to the surface of the slab is maintained in contact with the work surface during relative longitudinal movement between the head and slab in order that a substantially uniform depth of metal may be re moved and the gas efficiently used. The operating mechanism is so arranged and constructed that the head is pressed upwardly into contact with the bottom slab surface at a substantially uniform pressure irrespective of changes in the level of the surface and irrespective of any warp or twist of the slab. The head may be raised to or lowered from the operating position adjacent the work and the'machine may be moved transversely out from under the conveyor line whenever desirable.

Desurfacing the bottom surfaces of slabs instead of the-top surface has been found to present numerous advantages; the molten slag does not flow over the edges to form undesirable fins;

.the slag quickly falls away from the bottom surface and does not tend to pile up or collect in front of the nozzles and clog the nozzles or form deposits on the surface; the disposal of the slag which falls away from the bottom surface does not involve the considerable difficulties which are involved in the disposal of the slag which pours over the trailing end of the slab when removing metal from a top surface; the bottom surface is always at the same level except for a relatively small change of level caused by deformation of the slab, whereas, when desurfacing the top surface, the level of the upper surface varies according to the thickness of the slab; and, the desurfacing machine may be more economically supported.

Accordingly, the principal objects of this invention are to provide improved procedure and apparatus for surface conditioning the entire bottom surface of a metal body; to provide such process and apparatus particularly adapted for removing a layer of surface metal from the bot=- tom surface of a ferrous metal body, while such body is at a rolling temperature and at a point between successive rolling operations; to provide such an apparatus which may be installed beneath an existing conveyor table of a steel mill; to provide a raising and lowering mechanism for resiliently supporting the blowpipe head, for urging the blowpipe head upwardly against the lower surface of the body with a constant pressure, and for maintaining. the blowpipe head in uniform contact with the steel body irrespective of the warp or twist of the body; to provide such apparatus which includes means for lowering the gas delivering unit before reaching the end of the steel body to prevent damage thereto by irregularities such as "rosebuds" or other irregularities at the end of the steel body; to provide such apparatus which includes means for retaining the steel body on the ,ofFig.12;' U

Fig. 14 is a fragmentary view similar to Fig. 13

roll table rollers irrespective of the upward pressure exerted by the gas delivering unit; to provide such apparatus which will eliminate the considerable difficulties of the slag disposal when desurfacing relatively large steel slabs; to provide such apparatus which includes an improved, water-cooled-shoe for contacting the surface of the steel body to maintain the blowpipe nozzles in operative relation to the surface and for protecting the blowpipe nozzles; and to provide a process for conditioning the surface of a metal body wherein the means for applying the gas is moved away from the body before the end of the body is reached and the flow of gas is continued to prevent slag adherence thereto.

These and other objects and novel features of this invention will become apparentfrom the following description taken in connection with Fig. 4 is a fragmentary view of the front of the hold-down 'means taken along "lined-4 of v Fig. 1; Fig. 5' is a I e v enlarged scale of the drive means taken along line 5-5 of Fig. 3;

fragmentary sectional view on an Fig. B is afragmentary sectional view on an: enlarged scale of the driven axle taken along line. i-'$ of Fig. 2; V.

Fig. 7isa view of a verticaljsection of the .desu'rf'acing machine taken along line 11-10121 Fi T v v Fig.'=8 is-aview of a, horizontal section through} the right-hand guide column taken along .line- 8-'-3ofFig.2';, 'Fig. 915 a fragmentaryview on an enlarged I 1 scale ofa-sectiont'aken along-line 9-4 of Fig. 8.:-

vthrough the right-hand guide column with the front, plate and guides removed;

Fig. IOQisa side elevationalview on an 'en- I Fig. 11 is a rear elevational view of 'the' head lof Fig. 10;

Fig.12 is'an enlarged fragmentary. detail view ;of the front of the head of Fig. 10; I e

. Fig. 13 is a view on an enlarged scale of a section through the head'taken along line l3-l3 taken along line I l-l4 of "Fig. 12; 1

Fig.l5 is a fragmentary view of a section disj closing the means for sealing the passagefor the end nozzles of each head which section is taken along line l5--i5 of Fig. 12;

.Fig. 16 is a fragmentary view of a section through the head disclosing the preheating gas passages and taken along line Iii-46 of Fig. 13;.

Fig. 17 is a similar view of a section through the head to show the cutting oxygen distributing chambers and taken along line "-41 of Fig. 13;

Fig. 18- is a fragmentary rear view of the desurfacing machine to show the means for tuming on and off the preheat gases;

Fig. 19 is a wiring diagram schematically illushating the electrical circuit of the/control means for operating this machine; and,

Y largedscale of one of the multiple nozzle heads and the-attached gas supplying apparatus;

.secured between the members 26.

' Fig. 20illustrates the sequential operation of the drum-type switch controller.

Referring to the drawings and particularly to Figs. 1, 2, and 3, the body to be surface conditioned may be a ferrous metal body such as a relatively wide steel slab 8 supported on the usual rollers 20 of a steel mill conveyor table C. The rollers 20 are mounted on axles supported in suitable bearings and the axles are connected through bevel gearing to the longitudinal drive shaft 2| which is driven by a motor in the usual manner, the gearing and motor are not shown in the interests of greater cleamess of the draw- .ing. The surface conditioning head shown generally at H is substantially equal in widthto the widest steel body to be surface conditioned and is attached to and supported by the carrier plate 23 which will be later described in detail. The

head H and carrier plate 23 are resiliently sup ported by and moved up and down ,by two air cylinders 25 cradled on the frame of a motor driven carriage Fmounted on transverse rails R.

formovement into and out of operative alignment beneath the conveyor table C. The rails R may be fastened'to the floor of the steel mill or to; any suitable-supporting base beneath the roll table-C. The slag formed by the thermochemical removal of the surface material is col- .lectedin the hopper W. disposed beneath the .slab S, and the hopper W will be later described in more detail.

Thebox-like frame of carriage F comprises ,two relatively long parallel side members 26 which are rigidly spaced apart, by cross-members 21. 'Near the right-hand end of members 26 there is secured to plates 26 a transverse up wardlyextending plate 28.: An upwardly extending left-hand plate 29,'sim ilar to plate 28, is also Secured 4 to side members 26 and plate 28, are a pair of up- .wardly extending frontand rear plates 30 and -a-,similar pair offront and rear plates 3| are secured to side members 26 and to the upwardly extending plate 29. Plates 30 and 28 form the partially-enclosed right-hand guide column J, .and plates 3|and 29 form thejleft-hand guide ,column J.

The top of the columns'J andJ' may be closed by .covers 32 to protect'the' mechanism therein from-dirt and other foreign materials. e

The carriage F is supported on the rails R by four wheels 33 which are mounted on the outer ends of two transverse axles 34 (Fig. 6), extending through plates 3| and through side members 28. The axles 34 are mounted in bearing 35' secured against the outside faces of members .26.

The wheels 33 are protected against dirt, dust and slag by covers .36 fastened to members 26. Only the left-hand axle "34 is motor-driven and to this end there is mounted centrally thereon a worm gear 31 whichmeshes with a worm 38,

formed integral withor' mounted on a shaft 39, supported by bearings 40 in the cross-members 21 (see Figs. 5 and 6). The shaft 39 is connected to the output shaft, of a speed reducer 4| of a motor unit 42 by a flexible coupling 43 (Fig. 13).

Motor 42 supplies themotive power for moving the surface conditioningmachine along the rails R to a position beneath the roll table C or to a position out of operative alignment with the roll table. An electrical solenoid-operable brake shown generally at B is mounted in the frame F g and when the electrical circuit to the motor 42 is closed to energize the motor, the solenoid of brake B is energized so that the brake does not engage the rearwardly extending portion of the motor shaft but when the electrical circuit is broken the laws of the brake B grip the motor shaft and prevent the desurfacing machine from moving from its position.

Referring more particularly to Figs. 1 to 3 and 7, the surface conditioning head H is mounted on the upper ends of two piston rods 24 of the air cylinders 25 and is supported and moved upwardly anddownwardly by the pistons operating in the cylinders 25. On cross members 21 there are three bearings 44 in which are pivotally mounted outwardly extending and axially aligned trunnions 45 of two cradle members 45. The

' cradle members 45 are therefore rockable about a horizontal transverse axis. The front member 28 may be cut away as more clearly shown in Fig. 2 to allow cradle members 46 to rock forwardly. Each of the two air cylinders 25 has a pair of trunnions pivotally mounted in bearings 47 on cradle members 46. The axes of the bearings 41 are perpendicular to the axis of the cradle trunnions. Thus each air cylinder 25 and cradle member 46 can tilt fore and aft in bearings 44 and each air cylinder 25 individually can tilt to the. left or right in bearings 41. When air is admitted under pressure to the head ends of cylinders 25 and under the pistons therein, the surface conditioning head H is raised, and when the air pressure is released the head H is lowered,

due to its weight.

On the upper end of each piston rod 24 there is fastened a clevis 48 which is pivotally secured to a horizontal pin 49, (Fig. 7) by a transverse pin 55. On the carrier plate 23 of the head H there are two pairs of depending brackets i and in each pair of brackets one of the horizontal pins 49 is pivotally mounted so that the carrier plate is tiltable relatively to the piston rods 24 both fore and aft and laterally.

Guiding means are provided in right and left columns J and J for normally maintaining the surface conditioning head H in a vertical position but allowing the head to tilt or cant to the right or left to follow the surface of a twisted or warped slab. As both guide columns are the same except that one is left-hand and the other right-hand, only one will be described in detail. To each end of the carrier plate 23 there is fastened a bracket member 53. The right-hand bracket member 53 extends into the guide column J, as more clearly shown in Figs. 8 and 9, and has pivotally mounted thereon seven rollers which contact vertical guide member in column J.

In column J there are four vertical guide members 54, 55, 56, and 57. Mounted on horizontal pins 58 in member 53 extending transversely from the upper and lower corners thereof are a pair of rollers 59 which may contact either a guide surface 68 or iii of the guides 54 and 55, respectively. The guides 54 and 55 coact with the similar guides in guide column J to hold the carrier plate in the vertical position with respect to fore or aft deflection. The distance between the guide surfaces 60 and 5| is slightly greater than the diameter of rollers 59 to lower the friction and work required to raise the surface conditioning head H. By adjusting screws 52 extending inwardly through the plates 30 the guides 54 and 55 may be moved to adjust the distance betweenthe guide surfaces 80 and 6!. Also mounted intermediate between and perpendicularly with respect to pins 58 in member 53 is a pin 52 on the outer end of which is mounted a roller .43 which contacts an edge guide surface 44 of the guide member 54. A similar roller in the guide column J contacts a similar guide surface to prevent any transverse shifting of the head H either to the left or right. The bracket 53 also carries horizontal upper and lower pins .normally contact their respective guide surfaces when the head H is in the upright horizontal position.

Roller 63 is vertically midway between the upper and lower rollers 68 and the upper and lower rollers 59. As the left-hand end of the carrier plate and the left-hand colum J are similar to the corresponding right-hand units, the head H cannot shift horizontally either to the left or right but can tilt or cant either to the left or right until the lower or upper pairs of rollers 81 and 68 contact the guide surfaces II or 13. Thus, the desurfacing head H can tilt to follow the lower surface of twisted, warped or bent slabs. The row of blowpipe nozzles in head H is always substantially parallel with the bottom surface of slab S so that a substantially uniform depth of metal is removed from the entire surface irrespective of surface inclination or slab warpage.

The carrier plate 23 may be fabricated by welding together preformed plates or may be formed by other suitable means to provide a member which is light in weight but of a rigid construction. The carrier plate is disposed below the slab and is not subject to as intense a degree of heat as it would be if disposed above the slab, but, it is preferable that the carrier plate be water cooled to prevent damage or warpage by heat. Carrier plate 23 is therefore provided with a chamber 12 having an inlet connection 69 (Fig. 2) through which cooling fluid is admitted to the chamber 12. The cooling fluid is discharged through two outlet connections 14 at each end wall and to the drain pipe 18.

As shown by the drawings, the desurfacing head H comprises a number of similar blowpipe heads 75, each containing a plurality of nozzles and means for supplying each head with suitable gases and cooling fluid. As all of the heads are similar, only one multiple nozzle head will be described in detail.

Each head i5 comprises a nozzle retaining or header block l6 and a removable nozzle protecting shoe ll. The head 15 is removably attached to the carrier plate 23 by bolts 19 and 19'. A clamp bar may be placed between the heads of bolts 19 and the head 15 as shown and, if only part of the bolts 19 are. tight the head 15 still is retained securely in place. In the block 16, there is a plurality of similar oxidizing gas passages 82 each of which is enlarged and threaded at its forward outlet end to operatively receive the inlet end of a nozzle 8i removably secured therein by means of a nozzle retaining nut 83. The inlet end of the passage 82 communicates with a V seating surfaces on the nozzle 8| to form gas tight seals. Between these seating surfaces the cavity in the block 16 is formed larger than the nozzle to provide the usual combustible or preheat gas distributing chamber at 88 for distributing a combustible gas mixture, such as oxygen and acetylene to the preheat passages in the nozzle. As disclosed in Fig. 16, a plurality of passages 88 may be drilled in the block I6 each communicating withra chamber 88. The passages 88 are so drilled that the inlet ends of each pair of passages intersect at the outlet end of one of the passages 90. The outer ends of passages 89 may be plugged with silver solder or other suitable means. The inlet end of each passage 80 is adapted to receive the threaded end of the blowpipe tube 8| of the blowpipe 82. The combustible gas is mixed in the blowpipe and flows-through tube 8I, passage 90, the two passages88 into the two chambers 88 and from each chamber 88 to the preheating passages of each corresponding one of the nozzles 8|.

.pair of nozzles 8|, there is provided a separate For each blowpipe 82, a passage 90 and two passages 89.

Theshoe I1 is attached to the block I6 by bolts 94 and 95 as more clearly shown in Figs. 13 and vli. .The bolts 94 extend through the shoe I1 and threadedly engage block I5. Bolts 85, are

- ins'erted= from the rear of block I5, and extend through one of the cooling chambers I and nozzle extends throughfa hole 85 in the front wall of the shoe TI and the forward end of the nozzle is substantially flush with the outer wall of theshoe. .To revent cooling fluid from leaking-past'thenozzle 8| to the outside of. the shoe, a 'pa'clring ring 9'I- which encircles the central portion 'of thefnozzle'is pressed against the inner front wall-surfaceof shoe I'I by'a compressed spring '88 surrounding the. nozzle. Each nozzle is retained in the headl 'l5 by similar means, but

because of, lack of space, the end' nozzles in each head "I5 are provided with slightly different packing as shown in Fig. 15. The end holes 86 are enlarged at approximately the central ,por-' tion and contain a. packing ring I00. The packing rings I00 fit the outer ,walls of the end noz- "zles tightly enough to prevent leakage of fluid past the nozzles. If there is enough space, the

end nozzles could be packed in the same manne as the other nozzles.

With this construction of the blowpipe head,v

the nozzles of each ,head 15 may be readily removed, all or singly, for replacement or inspecthreadedly'engage the shoe 11. To prevent leakage of cooling fluid fromthechamber past bolt 95,: a sealingor, packing sleeve 83 is provided,

4 A-gasket81-may-beprovided between shoe TI and block I5 to prevent leakage .of cooling fluid the'rebetween. Each nozzle 8| is retained in the block I8 by its nut 83. The;forward end of each and assembled' By loosening bolts I8. the head I5 may be readily removed as a unit for repair or replacement. 1

The heads I5 are in contact with the bottom surfaceof a usually hot slab and are in a zone of high temperature heat from the slab, the pre-' heating flames, the heat of the reaction and the hot slag. While the heads 15 are not exposed to as much heat as they would be if positioned on top of the slab, the heads and nozzles must be adequately cooled to prevent overheating. Each block I5 is adapted to receive a water inlet connection I03, and is formed with two transverse chambers I04 and I05 and is also formed with a cavity which coacts with a cavity in the sho TI to form the relatively large cooling chamber I05. A passage I01 connects the inlet I03 and chamber I04; passage I08 provides communication between chambers I04 and I06: and passage I09 provides communication between chambers I06 and I05. In the block I6 there is 'a bore I|2 adapted to receive the threadedconnection II 3 having attached thereto a length of overflow tubing II4 which extends from connection II 3 through bore II2 to substantially the top of chamber I05. Cooling liquid, such as water; flows from a supply tube I0 I, which is connected to a suitable source of supply, through connection I03, passage I01, chamber I04, passage I08,chamber I06, passage I08, into chamber I05 and out the overflow tube I I4 and through connection I I3 and tube II5 to the drain pipe I8. The cooling fluid chambers and connecting passages are so arranged that all portions of the head and nozzles are adequately cooled. The central portions of nozzles 8| are completely surrounded by cooling fluid and the gas passages 'and82 are 'well cooled to prevent overheating and possible pre By hav-" ing the inlet end of overflow tube II4 positioned ignition of the combustible gas mixture.

at the top of chamber I05, the chambers of the head are always maintained full oficooling fluid; The forward or front face of the nozzles 8|v are exposed to the heat but otherwise are fully en- I closed.

The number of nozzles in a head maybe any convenient number but as herein shown. and-de scribed, each head I5 comprises-a'nozzle heador in adjacent heads are so spaced that the individual oxygen streams from the nozzles intermingle so as to direct a substantially sheet-like stream I r of oxygen onto a transverse zone extending completelyacross the surface of slab/S. The surface of shoe 'I 'I which contacts the slab "is subjectto damage by abrasion, and to protect theshoe,

ridges of metal I I6 which areresistant to abrasion at high temperatures may be deposited on the slab contacting surface. Additionallyyto increase the useful life of the head I5; alayer o'f abrasion-resistant material may be deposited on w the shoe 11 and block 16 as is showngenerally at' Ill and H8, respectively. Asshown in Figskl3." and 14, the shoe 'II overlaps the forward corner of the block 16, as indicated at l8,"so that any force or shock on shoe "I1 is taken -by'the block ,I6 and. shoe 11 will not shift and damage the nozzles.

Across the back of the surface conditioning machine there is fastened a relatively large cutting mosphere, as would unheated water.

oxygen pipe I20 (Fig. 7) from which lead eight cutting oxygen lines Hi. There is a line I2I for each head I5 and the fiow oi cutting oxygen to each head may be controlled either by the manually operable valve I22 or the solenoid controlled valve I23 in each line IZI. Each oxygen line I2I is connected to an oxygen header I25 from which lead four lengths of tubing I26, each of which is connected to one of the four tubes 85, each tube 85 containing a manually operable valve 86. The preheat fuel gas, such as acetylene, flows by means of suitable lengths of pipe from one of the four acetylene supply lines I2? through one of the four corresponding acetylene valves I26 to a pair of manually operable valves I29. To each of the valves I 29 there is connected 2, length of flexible tubing I60 which in turn is connected through a suitable length of pipe and hose connection to an acetylene header I3I. Four lengths of copper tubing I32 lead from acetylene header ItI and each length of tubing contains a manually operable valve IM and is connected to one of the four blowpipes 92. Similarly, the preheat oxygen supply line I33 by means of suitable piping communicates with the four valves I34 and each valve I36 is connected to two manually operable valves I35 each of which is connected through a suitable length of tubing I63 to a preheat oxygen header I36. Each of the four lengths of copper tubing I317 communicate through a manually operable valve I 46 with the header I36 and with one of the blowpipes $2 to supply preheat oxygen thereto.

Also across the back of the machine are the cooling liquid supply and drain pipes'i38 and I35. Supply pipe I38 is connected to a source of constant temperature cooling liquid such as water and water flows from pipe I38, through a valve PM, flexible hose ItI and the length of copper tubing I62 to one of the blowpipes 92. The blowpipes 92 are connected by short lengths of tubing I65 and cooling water flows from one blowpipe to the next through tubes M6. Cooling water flows from the last biowplpe in each head through a length of tubing M6, hose connection Ml, hose M3, valve I49 and out through the drain pipe I39. The water for cooling the blowpipes is preferably heated to a low constant temperature so as to be at a constant temperature and not vary with the weather or temperature of the surrounding at- The cooling liquid supply pipe I50 supplies cooling liquid to the heads I5 and carrier plate 23. The supply pipe I59 communicates through a manually operable valve HI and a flexible hose I62 with supply tubes IDI of each head 7%. Cooling water fiows from pipe I56 through valve I5I, hose I62, tube Ifll, inlet connection I03 and through each head l5 and through the outlet line M5 to the drain I8. A pressure operated switch I50 may be connected to the supply pipe I56 so that when the pressure of the cooling water drops below a predetermined value the switch I50 will operat an alarm, such as ringing a bell or turning on a light, to indicate to the operator that the cooling water pressure is below a safe value and that there is an inadequate supply of cooling fluid. Switch I50 also may be so connected as to operate the preheat gas controlling means, which is described later, to turn oilthe preheat flames and/or may be so connected as to operate the head raising and lowering means, which is described later, to cause the head H to be lowered away from the slab S.

The gas, water, and air supply pipes which are mounted on the back of the machine are connected through lengths of flexible tubing I52 to dicator dial suitable sources of suppl (see Fig. 2 and Fig. 3). The lengths of tubing I 62 are flexible and of such a length as to allow the desurfacing machine to move along the rails R to a position beneath or to one side of the roll table. A supporting apron IE3 is provided at the left-hand end of the machine to support the flexible supply tubing I 52.

By means of the manually operable valves in the preheating acetylene and oxygen lines and in the cutting oxygen, line, the nozzles may be blanked ch in pairs, if for any reason it is desired to reduce the effective width of head H. Thus, when conditioning the surface of a slab which is narrower than the width of the head, the end nozzles may be blanked oil in pairs by means of valves I68, Md, and 88 so the effective width of the head His substantially equal to the slab. Normally, all manually operable valves are open and the flow of gases is controlled by electrically operable valves and the switch-means controlling all electrical operated valves may be conveniently located at a single point.

On the back of the machine there is positioned a relatively small air operated power cylinder I55 for each two heads (see Figs. 3 and 18). The piston rod IM of each air cylinder I55 is connected to the valve levers of an acetylene valve I28 and a preheat oxygen valve I3 5 for controlling the flow of preheat gases to two heads I5. The air lines wt and IN communicate with the ports of the four-way solenoid valve I56 and communicate with the head and rod ends of air cylinders 555. Air under pressure is supplied to the four-way valve I58 and when an electrical circuit to this valve is closed to energize the solenoid, the valve I58 is so positioned that air under pressure is supplied to line I55 and to the head end of each air cylinder I56, to raise all the pistons and open all of the preheat gas valves I26 and I 36. Si-

multaneously, the rod end of each air cylinder I55 and line I 5? is opened to the atmosphere and, when the solenoid valve I58 is de-energized, air under pressure is admitted to line I57 and the rod ends of air cylinders I55 to close valves I28 and I36, and line I56 and the head ends of the air cylinders are opened to the atmosphere. The four-way valve its simultaneously opens and closes all of the preheat gas valves and the pre heat gases separately flow to the blowpipes where the gases are mixed and the combustible gas mixture flows from the blowpipes to the nozzles, unless some of the gas lines are closed by means of the manually operable valves.

Suitable limit switches may be provided to prevent the desurfacing machine from moving too far along the rails R in either direction. It is essential that the desurfacing head H be correctly positioned beneath the slab S and as an aid in positioning the machine, a positionindicator M is provided. On a machine there is mounted an in- I6il (Fig. 2) having a pivotally mounted indicator pointer I6I which is connected by means of a pinion and rack to the vertical rod I62, positioned by suitable collars. On the lower end of rod I62 there is fastened a bracket I63 containing a roller I66 adapted for engaging the sloping surface of the adjustable cam I65. The cam I65 is positioned and proportioned so that as the machine approaches the correct position beneath the slab S, the rod I62 is raised and the indicator pointer I6I is moved through an arc across the dial I66 to indicate the position of the desurfacing machinerelative to the slab. The operator, while positioned at one side of the machine out of the zone of intense a heat, can readily see the indicator M and ascertain whether or not the desurfacing machine is in the correct position relative to the slab S. As

a further aid in positioning the desurfacing machine, a downwardly depending plate I81 may be provided on the carriage F. A stop I88 may also betprovided and secured between the rails B so that when the machine reaches its limit of movement towards the right, plate I81 will strike the stop I68 and stop the machines On each of the columns J and J? there may be provided a 1mm; switch no having an mwardly extending finger HI and which is so positioned that as the head H is moved upwardly toward the bottom of the slab one of the rollers 58 will strike the fingers "I to close the switches I10. When switche I are closed;

I the'circuit to the four-way solenoid valve I58 is energized to turn on the preheat valves I28 andl3'4. The switches I10 can be set so that .as the head H approaches the bottom of the circuit so that the preheating gases will be turned on a short time priorto lighting, to

purge the. blowpipes and gas lines and prevent backfire which is very undesirable. In addition. thellimitswitches I10 are preferably positioned so" as toturn the preheating gases off after the head H has been withdrawn downward a. short distance from the surface of the slab to eliminate a slight amount and the pressure is not mateany possible chance of molten slag clogging the blowpipe nozzles.

Air under pressure is supplied from a suitable source to one of the flexible hoses I52 connected to the supply line I13 which is divided into two branch lines I14 and I15. Air line I18 is con- 7 nected to the four-way valve I58 to supply air for operating the preheat gas valves. At a T connection I18, the air line I15 is split into two lines I11and I18, each of which contains a pressure regulator I18 and a pair of manually operable valves I80 on each side of the regulators. The regulators I18 maintain the pressure ofthe air delivered to a common line I8I within fairly close limits and by means of the valves I80 either one of the lines I11 and I18 may be closed should one of the regulators become inoperative. A pressure indicator I82 may be provided to visually indicate the air pressure in linel8l. Air line I 8I is branched into two air lines I83 and I84.. Line .I83 has interposed therein the electrically-operable solenoid valve I85 which is operable through suitable switch means by remote control such as at a remote control table. When the electrical switch of valve I85 is closed, the solenoid of valve I85 is energized to open the valve against spring pressure .which normally closes the valve when sure flows from line I83 through valve I85, a line I88 and short lengths of flexible hose I81 to thebottom or head ends of cylinders 25,

thereby raising the head H toward the slab S.

Branch air line I84 communicates with alarge air receiver tank I88 and when solenoid valve riall'y'increased as it would be if tank I88 were omitted. A suitable safety valve I80 is operatively connected to tankl88 and is so constructed that it may be adjusted to open when the air pressure in .tank I88 exceeds a predetermined safe pressure and to close or remain closed when the air pressure in tank I88 is below the predetermined safe pressure. If the pressure in tank I88 surpasses a redetermined value, safety valve I80 automatically opens and air is exhausted to the atmosphere through the vent tube of valve I80 and, when enough air has been exhausted from tank I88 so that the pres- I sure in tank I88 is at or slightly below the predetermined value, safety valve I80 automatically closes. Thus, the pressure in tank I88 is maintained within safe limits. A normally open, electrical solenoid operated, relief valve I8I is provided to'aid'in maintaining a substantially constant air pressure in line I86 and for venting air-from the cylinders 25 and line I88 to lower the head H. A relatively small air tube I82.

maintain the pressure in cylinders 25 within 6' oz. per sq. in. of the correct pressure. By means of a manually operable vent tube valve I85 the rate of flow at which the air is exhausted may be readily controlled. When enough air has been exhausted so that the pressure in line I88 is at the desired value, the switch in housing I83 closes and energizes the solenoid valve I8I thereby closing the valve. Valve I 85 is normally closed and valve I8I is normally open, thus air pressure can only build up in the cylinders 25 to raise the head when the electrical circuit to these valves is closed to energize the solenoid of each valve. Bymeans of regulators I18 and the solenoid valve I8I and its control switch in housing I83, the air pressure in cylinders 25 and air line I88 can be maintained within very close limits. When the head H is raised, it is urged upwardly into contact with the bottom surface of slab S with a force only slightly greater than necessary 7 to raise the head, therefore the head willfollow and assume a position normal to the bottom surface of warped, twisted and irregular slabs. If

v the pressure of head H against the slab surface the solenoid is not energized and air under pres- 7 is slight, the heads can readily be forced downward to follow the surface thus preventing or minimizing damage to the head and the wearingv I away of the nozzle shoe is reduced to a minimum. To lower the head H, the solenoid valve I85 is' deenergized, thus closing the valve to prevent air from entering line I86 from line I83, and the solenoid valve I8I is deenergized to open the valve and vent air through the tube I84 to th atmosphere. The weight ofthe head H causes the pistons in cylinders 25 to lower. The upper. or rod ends of cylinders 25 are open to the atmosphere to prevent the creation of a vacuum or pressure which would interfere with the raising and lowering-of the head H. To prevent the upwardly urged head-H from lifting the slab .S from rollers 20 and more particularly to maintain the slab in contact with'the rollers adjacent the head H, a

sealants hold-down roller I96 is pivotally mounted above the slab S and substantially above the head H as shown in Figs. 1 and 4. The roller I98 extends across the slab and may be pivotally supported at each end in vertically slidable blocks 22B mounted in members I88 which may be in turn mounted on each side of the roll table support. The roller I98 is resiliently pressed downward by the springs 2M and holds the slab S in contact with the roll table rollers 20 which are adjacent the head H and maintains the slab in the correct position for desurfacing.

In the frame of a carriage F there are mounted two heavy coil springs it? each confined within a casing I98 (Figs. 2 and 9). A cap I99 is mounted on top of each coil spring i9? and is slidably confined in the upper end of the casing I98. To the bottom of the carrier plate as there are fastened two downwardly depending members 200 and when the head is in the lowered position, each member ziiil rests on a corresponding cap I99. Thus, the coil springs i9? resiliently support the head when in the lowered position and act as shock absorbers if the head is lowered suddenly.

As shown in Fig. l, beneath the conveyor and the slab S there is pivotally supported in member 282 a horizontal transverse shaft 203 on which there is mounted an arm and the outer end of which carries a shoe 2% normally con tacting the bottom surface of the slab S. Also on shaft 263 is arm are which may be separate from or an extension of arm are so that arms 20d and 206 in effect form a bellcrank. The outer end of arm 2% contacts a pressure exerting member, such as a spring contained in member 287, so that shoe 205 is urged upwardly against the slab S. On shaft 203, there is mounted a switch operating arm ate, so positioned that when shaft 203 turns, arm 208 either opens or closes the electric switch 299. When the final or leavin end of slab S passes over the shoe 285:, the arm 20 3 swings upwardly and moves arm 208, thereby operating the switch 2% which is connected in such a manner to the solenoid valves I85 and i9! as to automatically lower the head H. It is preferable that an electrical time delay device be interposed in the electrical circuit of switch 209 so that the head H will not start to lower until the end of the slab is a predetermined distance from the nozzles. The ends of slab S are usually very irregular in shape and are subsequently removed. If such an end should strike the head H, while it was being urged upwardly against the slab, serious damage to the head may result. By

correctly positioning the arm 2% and by cor= rectly setting the electrical time delay device, the head H can be lowered far enough away from the slab so as to prevent or minimize any possible damage to the head H, and even though an irregular slab should strike the head, the head would probably not be damaged if moving in a downward direction. When head H starts to lower, the preheating flames and the oxidizing gas are preferably left on for a short length of time which prevents clogging of the nozzles and additionally aids in completely or nearly completely desurfacing the slab.

A shock absorber 2l2 may be mounted on the roll table frame, or on other suitable means, as shown in Fig. 1. Because of imperfections in the surface of the slab, the friction between the slab S and head H may become great enough to cause the machine to tilt in the direction of slab movement. Additionally, the head H may be subjected to impact from downwardly turned, trailing slab ends. If such friction or impact is great enough to tilt the machine, an outwardly erate the switch to break the electrical circuit of the roll table motor to stop the movement of the slab, or to break the circuit to the solenoid valves E and Edi as shown in Fig. 19 and thereby cause the head to lower, or to do, both. Thus, the shock absorber M2 is a safety means for preventing damage to the machine by absorbing the impact of deformed slabs against the head H and by relieving the friction between head H and slab S.

During the desurfacing operation, the oxidizing gas reacts with the surface material of the slab S to produce molten slag mixture which falls away from the bottom surface of the slab in a curved path. A hopper W is provided beneath the conveyor C to collect this molten slag. In

the hopper W, a number of water sprays 215 are provided to maintain a film of water on the surface of the sidewalls and the bottom 2N5 of hop per W. When the molten slag impinges on a wet surface, a blanket of steam is formed between the surface and the slag which prevents the slag from adhering to the surface. Thus, a large part of the molten slag impinges on the hopper wall 2m which acts as a slag shield and the slag falls to the bottom of the hopper either as a solid or as a liquid which is quickly cooled by the water. The slag collects on the bottom lid of hopper W in the form of porous particles or lumps of solid slag. Streams of water may be directed across the bottom 286 to wash the sla through the opening 25'? in the side of the hopper into the chute 2E8 which may lead to a pit where the slag may be collected in buckets and where the water may enter a drain. The slag, after collection may be reclaimed by smelting in a usual manner. The slag quickly falls away from the bottom surface and does not tend to pile up on the surface and clog the nozzles or flow over the sides to form fins or flow over the trailing end as when desurfacing atop surface.

When desurfacing from the bottom the disposal of the slag does not involve the considerable difficulties which are involved in the disposal of the slag which pours over the trailing end when removing metal from a top surface.

It is preferable that this machine be controlled by means of electrical switches located at a remote point such as ata remote control table out of the zone of high temperature heat. A plurality of switches may be sequentially operated to operate this machine but it is preferable that a single sequentially operable switch be used. A sequentially operable drum-type switch similar to that disclosed in the United States application, Serial No. 272,555, filed May 9, 1939 by James H. Bucknam now issued as Patent No. 2,244,822 is suitable for controlling this machine.

Fig. 19 is-a wiring diagram schematically illus trating the electrical circuit of the control means for operating this machine. Fig. 20 illustrates the sequential operation of the drum-type switch controller, through the five positions and the ofi" position, and along with Fig. 19, illustrates chine. All non-essential elements have been eliminated from Fig. 19 to shown more clearly the essential elements. The drum-type switch controller is provided with eight contacts designated'al through hI, inclusive, which are all connected to the line LI except contact yl and which are brought into proper sequential engagement with corresponding contacts-a2 through h2 to correctly operate the machine.

With the drum-type switch controller in the on position, as shown in Fig. 19, only the contacts al, a2 and bl, b2 are closed and the operator by means of push button switches 225 and 226 can cause the desurfacin machine to move into or out of alignment with the roll table. A limit switch 229 may be provided in the motor circuit for limiting the inward movement of the machine and a limit switch 230 preferably is provided in the circuit of motor 42 for limiting the outward movement of the machine. When the machine is in the outward position, at one side of the roll table, the limit switch 230 is open and the limit switch 229 is closed so that the operator by actuating the push button switch 225 can complete the electrical circuit from LI through line 232 and the carriage motor 42 to L2 to cause the machine to move inwardly and into alignment with the roll table. This inward movement is limited by the stop I 68 and/or the limit switch machine is not in the outward position, the out limit switch 230 is closed and the operator by actuating the push button switch 226 can complete the electrical circuit from LI through line 233, and the motor 42 to L2, to cause the machine to move outwardly until stopped by the opening of the limit switch 230. One or the other of the limit switches 229, 230 is always in the closed position. A push button switch 235 is preferably provided in the carriage motor circuit so that the circuit can be broken and the machine stopped at any time.

Additionally, when the drum-type switch con troller is in the off position, contacts bl, b2 are closed and the separate r011 table controlling switch 236 may: be operated to selectively cause the roll table motor, indicated at 231, to rotate' in either direction to move the slab S either forwardly or rearwardly as may be desired or to move the slab into position for the desurfacing operation to be started. The roll table control switch has forward, reverse and off positions. The contacts al, a2, bl, D2 are closed only when the drum-type switch controller is in the off position so that the carriage cannot be moved transversely of the roll table and the slab cannot inadvertently be moved along the roll table when the head H is in the raised or operating position, thus preventing damage to the blowpipe head 11.

With the controller moved to the first position, the contacts dI, d2 are closed to energize the solenoids of the solenoid operated valves I85-and I9I to close the valve I9I and open valve I85'to admit air under pressure into the cylinders '25,

thereby raising the blowpipe head upwardly and into contact with the bottom surface of the slab S. The contacts fl, f2 are preferably closed, in which event, the closing of the two limit switches I10 completes the circuit of the solenoid operated'valve I58 to automatically turn on the preheat gases before the head contacts the slab. If desirable, the controller may be so constructed as to not close the contacts fl, f2 when in the first positionso that the preheat gases are not autocontacts fl, f2 and gl, g2 closed, the circuit of the solenoid operated valve I58 is closed so that 'the preheat gases are turned on if these gases have not been automatically turned on by the upward movement of the desurfacing head.

After a short preheating period to raise a portion of the surface metal to the oxygen ignition temperature the controller is moved to the third position which additionally and simultaneously closes the contacts cl, c2, and hl, h2 and preferably closes the contacts el, e2. With the contacts cl, c2 closed the forward circuit of the roll table motor is completed and the roll table motor is so energized as to move the slab forwardly along the roll table past the desurfacing head. The closing of the contacts M, M energizes the solenoids of the eight solenoid operated valves I23 to turn on the cutting oxygen. The contacts dI, 032 remain closed when the controller is in the third position, and if desirable, the normally closed switch 238 may be provided on--the roll to tilt, the projecting member 2I3 will open the normally. closed switch 238 and tie-energize the solenoids of valves I85, I9I to cause the head to be lowered. Also, when the controller is moved to the third position the contacts eI, e2 are closed so that the trailing end of the slab S by releasing the upwardly urged arm 204 actuates the limit switch 209 to energize the adjustable time delay mechanism TD. After a predetermined period has elapsed, the time delay mechanism TD energizes the relay 240 to open the normally closed switch 24I to break the electrical circuit of valves I and I9l. When the switch 2 is opened by the relay 240 the solenoids of the valves I85 and downward movement of the blowpipe head does 7 not turn ofi the preheat gases.

The fourth position is provided on the controller for more particularly causing the blowpipe head to move downwardly so that if for any reason it is not desirable to move the head automati- 1 cally downwardly through the operation oflimit switch 209, the blowpipe head can'be moved downw'ardlyby means of the controller. When the controller is in thefourth position the contacts-ell, d2 are open which dc-energizes the solenoids of valves 185, and I9I and preferably the contacts cl, 02 remain closed so that the slab will continue to move in a forward direction along the roll table. Also, if desirable the'contacts fl, 2, and gl 92 may be kept closed so that the preheat gases are left-on and the contacts hl, 712 may be closed to leave on the cutting oxygen.

With the controller in the fifth position all of the contacts are preferably open and the solenoid of the preheat valve I58 and the solenoids of the cutting oxygen valves I23 are all de-energized to turn off all of the gases. If desirable the contacts bl, 222, can be closed by the controller when in the fifth position so that the operator by actuating switch 238 can control the roll table motor to move the slab along the roll table in the desired direction. From the fifth position the controller is moved to the off position and only the contacts al a2 and bl, D2 are closed and the operator can, by means of the push button switches 225, and 228, cause the desurfacing machine to move transversely of the roll table and by means of switch 238 can cause movement of the slab along the roll table in the desired direction, all in the manner previously described.

When the slab S is correctly positioned on the roll table C and the surface-conditioning machine is in the operable position beneath the roll table, the control switch may be moved from the 011" position to the first position to energize the solenoid valve l85 thereby moving the head H upwardly and urging it upwardly against the bottom surface of a slab. The upward movement of the head H may operate the switches I10 on columns J and J to turn on the preheating gases, or, to turn on the preheating gases and either immediately, or after a, delay of a predetermined length of time, ignite the gases. If the switches H are not employed, the preheating flames may be turned on by moving the drum control switch to the second position. After a short preheating period during which the preheating flames are directed onto a relatively narrow transverse zone extending substantially across the slab and ad- Jacent to the starting end thereof, the control switch may be moved to the next position to turn on the cutting oxygen and simultaneously to start the roll table to move the slab relative to the head H thereby desurfacing the bottom slab surface. As the final end of the slab approaches the head, the arm 204 will be released to operate switch 209 and after a predetermined period has elapsed, solenoid valves I85 and HI will be deenergized to lower the head. As the head lowers, the preheating flames will be left on until the switches H0 are operated to turn off the preheat gases and, the control switch preferably is not operated immediately so that the oxygen is left on to completely desurface the head. If preferable, the head may be lowered and the preheat gases and the cutting oxygen turned off by moving the control switch through two additional positions as previously described.

After the bottom surface has been desurfaced, the slab may be turned over and run rearwardly along the roll table above the machine until the starting end is reached. The machine then may be operated to remove the defective metal from this second surface as previously described. Instead of making two passes to desurface the top and bottom surfaces, this machine may be used with other machines such as the desurfacing machine described in the copending application, Serial No. 255,398, filed February 9, 1939 by James H. Bucknam, Alfred J. Miller, and Arthur M. Keller now issued as Patent No. 2,200,259 for simultaneously removing defective surface metal from both the top and bottom surfaces at each ass. p Obviously, certain features of this invention may be used independently of others and changes may be made in various parts of the apparatus without departing from the spirit or scope of the invention.

For example, although as herein dis- [5 closed, the apparatus and process are especially adapted for desurfacing semi-finished relatively wide steel slabs while they areat a red heat and in transit between successive rolling operations, it will be understood that the same principles are applicable to the desurfacing of relatively narrow steel billets, blooms, and the like which are cold or at ordinary atmospheric temperature. In addition, this apparatus could be used for directing gases, such as heating flames onto the surface of a body for removing scale therefrom. Furthermore, other types of blowpipes may be employed to progressively apply wide streams of gas obliquely against and lengthwise of the longitudinal surfaces undergoing treatment.

What is claimed is:

1. In apparatus for conditioning the bottom surface of an elongated metal body such as a steel slab, a roll table for supporting and moving said slab, and a blowpipe machine disposed completely below said slab and said roll table and including a frame; a blowpipe head adapted to project a substantially sheet-like stream of gas against the bottom surface of said slab; and pneumatic raising and lowering means for supporting substantially the entire weight of said head on said frame and for urging said head upwardly against said surface.

2. Apparatus for thermally conditioning the surface of a metal body such as a steel slab comprising, in combination, a blowpipe head adapted to project gas against a surface of such a body; means for supporting said slab in a position for surface treatment; a frame for supporting said head; at least one cylinder adapted to raise and lower said head and for urging said head against said slab with a substantially definite predetermined force; and means for supplying gas at a substantially exact predetermined pressure to said cylinder, said means including a source of gas supply under pressure, a tank adapted to maintain a relatively large volume of gas therein, a valve for controlling the flow of gas from said source and said tank to said cylinder, and a relief valve for automatically venting gas from said cylinder and said tank when the pressure in said cylinder exceeds said predetermined pressure.

3. Apparatus for surface conditioning a metal body such as a steel slab comprising a blowpipe head adapted to project a stream of gas against a surface of said slab; a frame; raising and lowering means for supporting said head on said frame and adjacent and in sliding contact with said surface; power-actuated means for supporting said slab in a position for surface treatment and for moving said slab relative to said head, said head being so supported that excessive friction between said head and said slab may move said head in the direction of said slab movement; and, a mechanism operable by movement of the head in the direction of said slab movement for automatically relieving the friction between said head and said slab.

4. Apparatus for conditioning the surface of a metal body such as a steel slab comprising a blowpipe machine including a blowpipe head adapted to project a substantially sheet-like stream of gas against a surface of said slab, and raising and lowering means for supporting said head adjacent said surface; means for moving said slab relative to said machine; and a switch mechanism operable by relative movement past the final end of said slab for automatically initiating movement of said head away from said surface before said final end reaches said head.

5. In apparatus for thermally conditioning the surface of a ferrous metal body such as a steel slab, a blowpipe head having nozzle means adapted to project gas against the bottom surface of such a body, the head being of sufficient width to project gas on a narrow transverse zone of said surface extending substantially completely across said surface; means for supporting said slab above said head in a position for surface treatment; means for effecting relative movement of said slab and said head; a frame for supporting said head; raising and lowering means for supporting said head on said frame and for urging said head upwardly against said slab with a force in excess of the weight of the head; and switch means for automatically turning on the gas flow before said head contacts-said slab to purge the nozzles and gas supply lines thereby reducing the tendency for backfiring.

6. In apparatus for thermally conditioning the surface of a ferrous metal body such as a steel slab, a blowpipe head having nozzle means adapted to project gas against the bottom surface of such a body, the head beingof sufficient 1 width to project gas on a narrow transverse zone venting slag from adhering to the outlet ends of said nozzle means.

7. In apparatus for thermally conditioning the surface of a metalbody such as a steel slab, a blowpipe head having nozzle means adapted to project gas against the bottom surface of such a body, the head being of sufficient width to project gas on a narrow transverse zone of said surface extending completely across the surface; means for supporting said slab above said head in a position for surface treatment; means for efiecting relative movement of said slab and said head; a frame for supporting said head; raising and lowering means for supporting said head on said frame and for urging said head upwardly against said slab with a force in excess of the weight of the head; a hold-down roll supported above the slab to urge said slab downwardly and into contact with the rollers adjacent said head; and means for adjusting the force with which said roll urges said slab downwardly.

8. In apparatus for thermally conditioning the surface of a ferrous metal body such as a steel slab, a blowpipe head having nozzle means adapted to project gas against the bottom surface of such a body, the head being of suflicient width to project gas on a narrow transverse zone of said surface extending substantially completely across said surface; means for supporting said slab above said head in a. position for surface treatment; means for effecting relative movement of said slab and said head; a frame for supporting said head; raising and lowering means for supporting said head on said frame and for urging said head upwardly against said slab with a force in excess of the weight of the head; switch means operable upon the relative movement of the final slab end past such switch means for initiating the downward movement of said head away from said surface before said final end contacts said head.

9. In apparatus for thermally conditioning a surface of a metal body such as a steel slab, a

blowpipe head having nozzle means adapted to project gas against asurface of such body; means for supporting said slab in a position for surfacing treatment; a frame for supporting said head; means for effecting relative movement of said slab past said head; raising and lowering mechanism for supporting said head on said frame; and, means for automatically shutting off the gas flow to said head only after the head has been moved a predetermined distance from said surface, thereby preventing slag from adhering to the outlet ends of said nozzle means. v

10. Apparatus for thermally conditioning the surface of a metal body such as a steel slab comprising, in combination, a blowpipe head having nozzle means adapted to project gas against the bottom surface of said body, said head being of sumcient width to project gas against a zone of said surface extending completely across the surface, and, said head comprising a row of header blocks each carrying a row of nozzles and a nozzle shoe removably attached to each of said blocks and completely enclosing the nozzles except the orifice ends thereof; a conveyor for supporting said slab above said head in a position for surface treatment and for moving said slab relatively with respect to said head; a frame; column means on said frame for separately guiding each lateral end of said head, said guiding means being constructed and arranged to confine movement of said head in a plane transversely of said body and normal to said surface; a pair of air cylinders rockably mounted on said frame and connected to said head for raising and lowering said head; switch means operable by vertical movement of said head for automatically turning on the gas flow before said head rises into contact with said slab and for automatically shutting off the gas flow after said head has been lowered a predetermined distance from said slab; switch means operable by the movement of the final end of said slab past said switch for initiating downward movement of said head away from said surface; and, means for deflecting and collecting slag produced during the desurfacing operation.

11. In a machine for thermally conditioning the surface of a ferrous metal body such as a steel slab, a blowpipe head adapted to project gas against the bottom surface of said slab, the width of said head being sufllcient to project gas on a narrow transverse zone of said surface extending completely across said bottom surface; a supporting frame; guiding means on said frame for separately guiding each -lateral end of said head; and raising and lowering means mounted on said frame and connected to saidblowpipe head for moving and urging said head upwardly against said slab with a force slightly greater than necessary to overcome the weight of said blowpipe head.

12. In a machine for thermally conditioning the surface of a ferrous metal body such as a steel slab, a blowpipe head adapted to project gas against the bottom surface of said slab; the width of said head being sufllcient to project gas on a narrow transverse zone of said surface extending substantially completely across said bottom sur- 

